What gets me is all these big companies must spend small fortunes on customer service advisers, surveys, questionnaires etc, and on the whole customer service is worse than ever. The Mercedes dealer didn't even ring me back after I test drove a GLC, I did get a call from some nice lady a few weeks later asking if I was still interested. I told her I'd been forgotten about and had ordered a Porsche, she apologised and said her goodbyes.
The thing is, I assume you didn't order the Porsche simply because 'you'd been forgotten about'? you ordered the Porsche because you didn't want the GLC.
Surely a follow up phone call wouldn't have been enough to change your mind?
However, I agree it's bad practice not to call you after a test drive. Unless he/she made it clear that the ball was in your court so to speak.